# you do not refuse the one who is speaking

"you pay attention to the one who is speaking"

# if they did not escape

"if the people of Israel did not escape judgment" 

# the one who warned them on earth

Possible meanings are 1) "Moses, who warned them here on earth" or 2) "God, who warned them at Mount Sinai"

# if we turn away from the one who is warning

"if we disobey the one who is warning"